[PLASMA 5] Discover doesn't install apps to Plasma

[Steef]

I've had this problem with multiple applications but here I'll talk about Mattermost.
When I install Mattermost through Discover, Discover says it's installed but when I click Launch, nothing happens.
In ksystemlog I get the following:

12/26/24 7:30 PM    plasmashell    Failed to find service "com.mattermost.Desktop.desktop"​

Flatpak shows it as installed:

$ flatpak list | grep -i mattermost
Mattermost com.mattermost.Desktop 5.10.2 stable system

When I open the start menu and search for mattermost it shows it as uninstalled.

When I check the logs from installing Mattermost I get the following:

12/26/24 7:44 PM plasma-discover libostree pull from 'flathub' for app/com.mattermost.Desktop/x86_64/stable complete
security: GPG: summary+commit
security: SIGN: disabled http: TLS
delta: parts: 2 loose: 15
transfer: secs: 8 size: 105.0 MB

12/26/24 7:44 PM    plasma-discover    /var/tmp/flatpak-cache-HFR7Y2/com.mattermost.Desktop-9NN7Y2/repo-KBJjJ5: Pulled app/com.mattermost.Desktop/x86_64/stable from flathub

12/26/24 7:44 PM    systemd    var-tmp-flatpak\x2dcache\x2dHFR7Y2-com.mattermost.Desktop\x2d9NN7Y2.mount: Deactivated successfully.

​12/26/24 7:44 PM    flatpak-system-helper    system: Pulled app/com.mattermost.Desktop/x86_64/stable from /var/lib/flatpak/repo/tmp/flatpak-cache-TCR7Y2/repo-KBJjJ5

​12/26/24 7:44 PM    flatpak-system-helper    system: Installed app/com.mattermost.Desktop/x86_64/stable from flathub

[Steef]

I was able to find one person with a similar issue for a third party app but unfortunately they didn't provide more information:
https://github.com/vixalien/sticky/issues/104